1. Field of the Invention
The present invention relates to manufacture of a emiconductor. In particular, the present invention relates to a method and an apparatus for polishing using a CMP (Chemical-Mechanical-Polishing) technique for flattening a structural surface of a semiconductor device.
2. Background Art
In manufacturing a semiconductor integrated circuit device, several manufacturing steps of forming a diffusion layer in a silicon substrate wafer, forming an electric conductive film, patterning the film, forming an insulating film and so on are repeatedly conducted to thereby form semiconductor elements in the silicon substrate wafer. As a demand of manufacturing a highly integrated semiconductor integrated circuit device is increased, there has arisen a large problem of steps (unevenness) produced in a surface of the wafer.
A semiconductor integrated circuit including semiconductor elements is prepared by forming various thin films on a silicon wafer and removing unnecessary portions of the thin films by utilizing an etching technique or the like. In such process, a resist pattern used as a mask for etching is mainly formed by a lithography technique with use of a reduction projection exposure system in which an i-line or a KrF-excimer laser is used. However, as the number of thin films to be laminated increases, the degree of a step formed in the wafer increases whereby the depth of focus of the reduction projection exposure system becomes insufficient. Therefore, it becomes difficult to form the resist pattern by the lithography technique.
As a technique to make a surface, on which a resist pattern is formed, flat, a CMP technique is noted wherein a surface of a wafer is polished to flatten it during the processing. As an example of a method utilizing the CMP technique, there is such a method that in order to flatten the surface of an insulating film or an electric conductive film formed on an uneven surface of a wafer produced in the previous proceeding, an abrasive material composed of, for example, a mixed liquid of colloidal silica and potassium hydroxide (herein-below, referred to as slurry) is used to remove unevenness in the wafer surface as the result of the simultaneous effects of mechanically polishing and a chemical function.
As an apparatus for CMP, such one as described with reference to FIG. 7 has been used. Namely, a circular disk-like polishing plate 12 provided with a polishing pad 11 at its upper surface is rotated in a horizontal plane. On the other hand, a wafer-supporting table 15 holding a wafer 16 thereon is rotated during which the surface to be polished of the wafer 16 is pressed to the polishing pad 11. While the polishing plate 12 is rotated with respect to the wafer-supporting table 15, slurry is dropped from a slurry supplying section 14 through a supplying port 13 onto the polishing pad 11 whereby polishing is conducted.
The purpose of flattening the wafer surface is to avoid a shortage in the depth of focus in a process of light exposure using a stepper wherein exposure is conducted through a mask pattern to form a resist pattern. In this process, a region subjected to exposure once is about 15 mm square to 20 mm square. Accordingly, in the exposure process, it is sufficient if a wafer surface area corresponding to only one-time exposure (one-shot exposure) is flat. In consideration of this, Japanese Unexamined Patent Publication JP-A-8-162432 proposes a method for using a polishing pad having a diameter of several mmxe2x80x94several cm to conduct a CMP polishing operation for flattening each region corresponding to one-shot exposure.
The conventional polishing apparatus having the above-mentioned structure has, however, the problem as follows.
When the CMP polishing operation is conducted using the polishing apparatus to a wafer and if the wafer is large in diameter, there causes uneven polishing due to a difference of momentum applied to the wafer between a central portion and a peripheral portion of the wafer; unevenness in a pushing force to the wafer; and a difference of quantity of slurry to be fed between the central portion and the peripheral portion of the wafer and so on. This may cause a difference in the thickness of layered thin films.
Further, when the CMP polishing is conducted for flattening, marks used for exposure are also flattened, whereby reduction in accuracy of reading the marks may result.
Further, in the polishing method disclosed in JP-A-8-162432, it is necessary to form a space between adjacent exposed regions as shown in FIG. 8 because a square region corresponding to one-shot exposure must be flattened thoroughly without exception to corner portions by using a circular disk-like polishing pad. Accordingly, the presence of spaces between exposed regions adjacent to each other will reduce the number of devices to be formed on the wafer, and an expected number of devices obtainable from a single wafer is decreased, thus, productivity will decrease.
It is an object of the present invention to provide a method for polishing a semiconductor substrate wafer wherein a scattering of polishing on the surface of a large-sized wafer can be eliminated while reduction in productivity is prevented.
It is another object of the present invention to provide an apparatus for polishing a semiconductor substrate wafer wherein a scattering of polishing on the surface of a large-sized wafer can be eliminated while reduction in productivity is prevented, and the supply of slurry can uniformly and easily be conducted.
In accordance with a first aspect of the present invention, there is provided a method for polishing a semiconductor substrate wafer which comprises forming an insulating film or an electric conductive film on a semiconductor substrate wafer having an uneven surface which is produced in the previous proceeding, rolling under a pressure a polishing roller on a surface to be polished on said wafer whereby the surface to be polished on the wafer is made flat.
According to a second aspect, there is provided the method according to the first aspect wherein the width in a longitudinal direction of the polishing roller is formed so as to correspond to the width of a one-shot exposure, and polishing is conducted for each region of one-shot exposure.
According to a third aspect, there is provided the method according to the first aspect wherein a space is formed between adjacent regions to be polished, and a mark is arranged in the space.
In accordance with a fourth aspect of the present invention, there is provided an apparatus for polishing a semiconductor substrate wafer which comprises a wafer supporting table on which a semiconductor substrate wafer is placed, a polishing roller for polishing the semiconductor wafer, a slurry supplying mechanism for supplying slurry between the semiconductor substrate wafer and the polishing roller and a pressurizing mechanism for pressing the polishing roller to the semiconductor wafer to bring the roller into contact with the wafer.
According to a fifth aspect, there is provided the apparatus according to the fourth aspect wherein the width in a longitudinal direction of the polishing roller is formed so as to correspond to the width of a region of one-shot exposure.
According to a sixth aspect, there is provided the apparatus according to the fourth aspect wherein slurry is supplied for each time when a region of one-shot exposure in the wafer having been subjected to photoengraving is polished.
According to a seventh aspect, there is provided the apparatus according to the fourth aspect, wherein there are means for measuring a region to be polished in the semiconductor substrate wafer according to xe2x80x9cin-situxe2x80x9d observation and means for determining conditions of polishing on the polishing roller based on data obtained by measurements.
According to an eighth aspect, there is provided the apparatus according to the seventh aspect, a laser light is irradiated to a surface region to be polished of the semiconductor substrate wafer to measure a height of the surface of the semiconductor substrate wafer by utilizing interference of light.
According to a ninth aspect, there is provided the apparatus according to the seventh aspect, wherein light is irradiated to a surface region to be polished of the semiconductor substrate wafer to detect a change of the quality of an electric conducting film or an insulating film based on a change of an intensity or spectra of reflected light whereby the end point of polishing is determined.
According to a tenth aspect, there is provided the apparatus according to the fourth aspect, wherein a space is formed between adjacent regions to be polished, and a mark is arranged in the space.